Apparatus and method for increasing spin relaxation times for alkali atoms in alkali vapor cells

a technology of alkali vapor cells and spin relaxation times, applied in the field ofatomic vapor cells, can solve the problems of increasingaffecting the sensitivity of atomic vapor cell devices, and causing undesirable broadening of optical transitions, etc., to achieve the effect of reducing the relaxation rate of polarized vapor atoms, and improving the sensitivity o

Inactive Publication Date: 2012-05-10
RGT UNIV OF CALIFORNIA
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Benefits of technology

[0022]Polarization lifetimes of atomic populations and coherences in excess of 60 seconds in alkali vapor cells with inner walls coated with an alkene material are demonstrated. This represents two orders of magnitude improvement over the best paraffin coatings known in the art. Such anti-relaxation properties will likely lead to substantial improvements in atomic clocks, magnetometers, quantum memory, and enable sensitive studies of collisional effects and precision measurements of fundamental symmetries.
[0023]According to one aspect of the invention, a method for reducing the relaxation rate of polarized vapor atoms is provided that decreases relaxation due to atom-wall interactions, atom-atom interactions and atom-vapor source interactions.
[0024]Another aspect of the invention is to provide an atomic vapor cell wall coating that will preserve atomic spin polarization even after many impacts with the coating.
[0025]Another aspect of the invention is to provide an atomic vapor cell that isolates the vapor from the source of vapor and improving the rate of relaxation of the polarized atoms.

Problems solved by technology

The sensitivity of atomic vapor cell devices is generally limited by the number of atoms and their spin coherence lifetime.
While diffusion limited relaxation times of a few seconds can be achieved by this method, it also incurs additional relaxation via alkali-buffer gas spin-destruction collisions.
Furthermore, the additional buffer gas can produce undesirable broadening of optical transitions.
However, this is the upper limit for paraffin.
However, the performance of paraffin coatings quickly degrades at temperatures above 60-80° C. and it may not be available as a coating in some settings.
In addition, paraffin does not survive the elevated temperatures required by the anodic bonding process used in the production of microfabricated vapor cells.
In particular, a multilayer coating of octadecyltrichlorosilane [OTS, CH3(CH2)17SiCl3] has been observed to allow from hundreds up to 2100 bounces with the cell walls and can operate in the presence of potassium and rubidium vapor up to about 170° C. However, the quality of such coatings with respect to preserving alkali polarization is highly variable, even between cells coated in the same batch, and remains significantly worse than that achievable with paraffin.

Method used

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  • Apparatus and method for increasing spin relaxation times for alkali atoms in alkali vapor cells
  • Apparatus and method for increasing spin relaxation times for alkali atoms in alkali vapor cells
  • Apparatus and method for increasing spin relaxation times for alkali atoms in alkali vapor cells

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example 1

[0054]In order to demonstrate the longevity of Zeeman populations and coherences in alkali-metal vapor cells with inner walls coated with an alkene material, a room temperature magnetometer with cells coated with 1-nonadecene (CH2—CH(CH2)16—CH2) was used in the context of spin-exchange relaxation-free (SERF) magnetometry, a regime inaccessible with conventional paraffin coating materials. Coherences in excess of 60 seconds were observed with 3 cm diameter cells corresponding to approximately 1,000,000 polarization-preserving alkali-wall collisions. This represents approximately 2 orders of magnitude improvement over the best paraffin coatings.

[0055]Since the exchange of atoms between the bulb of the cell and the stem with the Rb reservoir can produce rapid relaxation, a “lockable stem” was employed that provided a coated barrier to reduce the rate of exchange between the vapor in the bulb and the stem as shown in FIG. 2. To investigate the alkene-based coating carefully, three Rb va...

example 2

[0064]To further illustrate the method for achieving long spin relaxation times in an alkene coated atomic vapor cell, numerical calculations were performed for comparison with experimental results from the apparatus that was constructed according the general schematic shown in FIG. 1. In order to compare the experimental results with the theoretical calculations it was convenient to plot the measured spin-exchange broadening ASE as a function of the effective gyromagnetic ratio γ, shown as triangles in FIG. 5. It can be seen that there is a linear relationship between the spin-exchange broadening and effective gyromagnetic ratio parameters, as indicated by the linear fit overlaying the data. It is also worth noting that, in these measurements, spin-exchange broadening approaches an asymptotic value of about 0.2 s−1 / μG2 at high power due to the presence of two isotopes, as can be seen by the clustering of data points at high light power, despite the increasing size of the light powe...

example 3

[0068]To demonstrate the adaptability and versatility of the coated atomic vapor cell for use in different types of magnetometry, a magnetometer was constructed for nonlinear magneto-optical rotation (FM-NMOR) magnetometry for evaluation. A typical NMOR apparatus includes an atomic vapor cell and two lasers, one for pumping the optical transitions of the atomic vapor of an alkali metal, in this case rubidium, and the other for probing the optical vapor, by differential polarimetry to detect the rotation of polarization. Electronics amplify the differential polarization signal and filter out noise, then condition the phase and amplitude for feedback to the pump laser. With the proper feedback, the magnetometer self-oscillates at a frequency that is a multiple of the Larmor frequency (or its harmonics). Counting the oscillation frequency over some period of time provides an estimate of the average magnetic field during that time. To enhance sensitivity, the atomic sample is held in a ...

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Abstract

An atomic vapor cell apparatus and method for obtaining spin polarized vapor of alkali atoms with relaxation times in excess of one minute is provided. The interior wall of the vapor cell is coated with an alkene-based material. The preferred coatings are alkenes ranging from C18 to C30 and C20-C24 are particularly preferred. These alkene coating materials, can support approximately 1,000,000 alkali-wall collisions before depolarizing an alkali atom, an improvement by roughly a factor of 100 over traditional alkane-based coatings. Further, the method involves a combination of one or more of the following: the use of a locking device to isolate the atoms in the volume of the vapor cell from the sidearm used as a reservoir for the alkali metal vapor source, careful management of magnetic-field gradients, and the use of the spin-exchange-relaxation-free (SERF) technique for suppressing spin-exchange relaxation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority from U.S. provisional patent application Ser. No. 61 / 409,004 filed on Nov. 1, 2010, which is incorporated herein by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]This invention was made with Government support under Grant No. N00014-05-1-0406 awarded by the Office of Naval Research, and under Grant No. PHY-0855552 awarded by the National Science Foundation. The Government has certain rights in this invention.INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC[0003]Not ApplicableBACKGROUND OF THE INVENTION[0004]1. Field of the Invention[0005]The present invention pertains generally to atomic vapor cells, and more particularly to method for achieving extremely long-lived polarization in alkali vapor cells with walls coated with long chain alkenes.[0006]2. Description of Related Art[0007]Long-lived ground-state coherences in atomic vapor cells fo...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G01R33/00
CPCG01R33/1284G01R33/26G01R33/282
Inventor BUDKER, DMITRYLEDBETTER, MICAHKARAULANOV, TODORBALABAS, MIKHAIL V.
Owner RGT UNIV OF CALIFORNIA
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